Environ Monit Assess. 2026 Apr 18;198(5):476. doi: 10.1007/s10661-026-15283-4.
ABSTRACT
This study presents a spatially explicit, seasonally resolved analysis of the intra-urban thermal heterogeneity in Chennai, a rapidly urbanizing tropical megacity along India’s southeast coast. Leveraging mobile environmental surveys across 81 georeferenced sites spanning six land-use zones, data on temperature, humidity, PM2.5, PM10, CO₂, and formaldehyde were collected during nighttime in summer and winter seasons. Thermal comfort was assessed using the thermal humidity index (THI), while spatial variability was visualized using GIS-based heat maps and inverse distance weighting (IDW) interpolation. Results revealed a pronounced summer intra-urban thermal contrast, with air temperatures in urban cores exceeding 32.5 °C compared to 31 °C or lower in vegetated suburban zones. In winter, central hotspots remained elevated at ~ 28.9 °C relative to peripheral regions (~ 25-26 °C). PM2.5 concentrations were significantly higher in summer (p = 0.00082), reflecting enhanced photochemical activity and dust resuspension under drier conditions. CO₂ showed a moderate positive correlation with temperature (R2 = 0.096, p = 0.0052), suggesting a potential climate-pollution feedback linked to anthropogenic heat emissions and increased energy demand. Analysis of thermal comfort revealed that 63% of surveyed sites were in the “torrid” discomfort category during summer, while the remaining 37% were “very hot.” Even in winter, 98% of sites were classified as “hot,” indicating persistent nocturnal thermal stress across the city. PCA indicated that temperature and pollution gradients jointly shaped the spatial clustering of intra-urban thermal hotspots, particularly in industrial and commercial zones. The study emphasizes the compounded impact of heat and pollution in shaping Chennai’s urban microclimates and highlights the need for climate-sensitive planning, urban greening, and adaptive infrastructure for tropical coastal Indian cities.
PMID:42000947 | DOI:10.1007/s10661-026-15283-4
